Cementing plug



R'. c. BAKER CEMENTING PLUG Filed oct. e. 195o Jan. 5, 1932.

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INVENTOR.

BY WX/07m mmf ATTORNEYS.

Jan. 5, 1932. Rf Q BAKER 1,839,861

cEEN'rmq PLUG Filed oct. s. 1930 2 s peetsL-neiet `l2 Eig@ IN V EN TOR.

Patented Jan. 5, 1932 NITED STATES PATENT OFFICE CEMENTING PLUG Application filed October 6, 1930. Serial No. 486,684.

This invention relates to apparatus for use in cementing oil wells and particularly pertains to a cementing plug such as disclosed in my Letters Patent of the United States :19': 1,392,619 issued-October 4, 1921.

In this prior patent I have disclosed a method of cementing a well which includes the steps of depositing a quantity of cement at the bottom of the well bore, securing a plug in the lower end of the well casing and then lowering the casing into the cement deposit so as to displace the same and force the cement upwardly about the casing.

It is the principal object of the present invention to generally improve devices of the character referred to whereby to provide an improved plug for well casings which is f1tted with mechanical means abutting against the lower end of the casing to prevent the plug from being forced upwardly into the casing.

rlhe present invention contemplates the use of a hollow plug member having a spheroidal lower end which is valved so that circulation of fluid is permitted therethrough while the plug is being lowered through the casing. The plug is tted with a packing gasket and with locking members so that after it has passed through the casing and drawn back therein the gasket will form a fluid-tight seal between the plug and the casing and the locking members will engage the lower ends of the casing so as to prevent the plug from being forced upwardly in the casing during the cementing operation.

One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which:

Fig. 1 is a view in vertical section through a well bore and well casing showing a plug embodying the preferred form of my invention being lowered therethrough, the plug being shown partly in elevation and partly in section.

Fig. 2 is a vertical section through a well bore and through a plug embodying/my inlvention after it has passed through the well casing and is being drawn upwardly into engagement with the casing.

Fig. 3 is a vertical section through a Well bore showing a plug embodying my invention in elevation as it will appear when positioned in place in the lower end of the casing just prior to the cementing operation.

Fig. 4 is a plan section through the plug taken on line IV--IV of Fig. 3.

Referring more particularly to the accompanying drawings` 10 indicates a Well bore in which a well Icasing l1 is positioned. ln 60 this instance the lower end of the casing is shown as fitted with a conventional type of casing shoe 12. Y

The plug embodying my invention comprises 'a hollow cylindrical shell 14 formed 65 with a spheroidal lower end 15. This lower cnd is formed with a concentric valve port 16 surrounded by a valve seat 17 with which a valve 18 cooperates. The valve`18 is secured on an v elongated valve stem 19 which 70 is guided in a bridge 20 in the lower end of the plug and in a guide tube 21 in the upper end of the plug. Intermediate its ends a cylindrical cam 22 is secured on the valve stem 19 and an expansion spring 23 is inter- 75 posed between this cam and the bridge 20, which spring normally tends to maintain the valve 18 seated.

Formed about the outer periphery of the upper end of the plug is a rubber packing 30 member 24. Secured to the upper end of the plug is a canvas packing gasket 25, which gasket is formed by a circular piece of canvas of such a. dimension as to provide a wide marginal extension as illustrated in the drawings. By means of this packing gasket it is possible to form asatisfactory seal between the interior surface of the casing shoe l2 and that portion of the plug 14 which is circumscribed by the rubber or packing member 24.

It should be stated that the exterior diameter of the plug 14 is of a diameter just'slightly less than the interior diameter of the casing and casing shoe so that the plug will be freely reciprocable therein.

l/Vhen the plug is finally positioned in the lower end of the casing shoe the packing gasket 25 is interposed between the packing member 24 and the interior bore of the cas- 100 ing. The it is a tight one so as to provide a fluid-tight joint.

Under some circumstances it is desirable to provide a mechanical medium for insuring that the lplug will not move upwardly in the casing after it is connected therewith and for this reason I have provided locking members 26. These locking members are radially disposed as illustrated and are arranged in cooperative position relative to the cam 22 on the valve stem 19. When the plug is being lowered through the well into position, the cam member 22 is out of register with the inner lends of the locking membersv26 but when the valve 18 is closed, which is the case when the plug is being drawn upwardly into the casing, the cam member will engage the inner ends of-the locking members 26 and move them radially outward to a position where they will engage lthe lower end of the casing shoe and prevent further movement of the plug upwardly into the casing.

In operation of the device, a quantity of cement in lastic form is deposited in the lower end of t e well bore and the well casino is elevated a distance above this material. 5Ihe plug is then inserted into the casing with the pac ing gasket upwardly directed and with the valve 18 in open position, so that the fluid may circulate upwardly through the plug` as the plug is being lowered in the casing. he valve is held in this open position against the action of the spring 23 by the weight of the tools connected with the upper end of the valve stem, which are the medium of lowering the plug in the well. In this position of course, the locking members 26 will be in t eir innermost position so that the plug may freely travel axially of the casing. l

The plug is then run entirely through the lower end of the casing and drawn back upwardly into the lower end of the casing shoe.

During this latter movement the packingmember 25 will be turned downwardly so as to embrace the upper end of the cylindrical portion of the plug 14. When the plug is drawn upwardly into the well casing or casing shoe, the thickness of the gasket and the dimensions of the`body member are such that a wedging action may be produced and a tight seal made between the interior of the casing shoe and the exterior of the plug.

However, the moment the plug commences its upward movement, the valve 18 will close and the cam 22 will move the locking members 26 outwardly. In this position, when the plug is drawn upwardly into the lower end of the casing shoe and pressure applied to the lower end of the plug, the locking members will engage the lower end of the casing shoe and prevent the plug from being moved upwardly into the casing. i.

When the plug has been properly positioned, the entire casing is lowered so that the lower end of the casing and plug will displace a quantity of the cement in the lower end of the bore and force it upwardly around the casing. After the cement has set, the plug is broken out in any suitable manner and the drilling is proceeded.

It will be evident from the foregoing descrption that various changes might be made in the general construction and arrangement of the parts of the preferred form of my invention without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claimand desire to secure by Letters Patent is:

1. A device of the character described comprising a plug adapted to be lowered through a string of well casing, said plug having a valve opening formed in its lower end, a valve stem extending coaxially through the plug, a valve on the lower end of the stem exterior of the plug for cooperation with said valve opening, a plurality of radially movable members normally disposed in an unobstructing position within the plug, cam means on the valve stem to engage said members when the valve is moved to closed position to project said members radially outward from the plug.

2. A device of the character described comprising a hollow plug of a diameter whereby it may be lowered through a well casing, said plug being formed with radial. sockets in the sides thereof, locking members positioned within said sockets and radially movable therein, said locking members being positioned when the device is being lowered in the casing with their outer ends within the periphery of the plug to engage the interior of the casing, said plug having a valve opening in its lower end, a valve member for cooperation with said opening, a valve stem connected to the valve member and extending axially upward through the plug, a cam member fixed on said stem within the plug to engage the inner ends of said locking members, said inner ends of said locking members preventing upward movement of the cam' when the device is disposed within the casing whereby to prevent closing of the valve, said locking members being capable of being forced radially outward by the vertical movement of the valve stem after the plug has passed through the casing whereby to close the valve and to project said locking members to a point where they will engage the lower ends of the casing and prevent upward movement of the plug back into the casing.

3. A device of the character described comprising a hollow plug of a diameter whereby it may be lowered through a well casing, said plug being formed with radial sockets in the sides thereof, locking members positioned within 'said sockets and radially movable therein, said lockingl members being positioned when the device is being lowered in the casing with their outer ends within the periphery of the plug to engage the interior of the casing, said plug having a valve opening in its lower end, a valve member for cooperation with said opening, a valve stem connected to the -valve member and extending axially upward through the plug, a cam member fixed on said stem within the plug to engage the inner ends of said locking members, said inner ends of said locking members preventing upward movement of the cam when the device is disposed within the casing whereby to prevent closing of the valve, said locking members being capable of being forced radiallly outward by the vertical movement of the valve stem after the plug has passed through the casing whereby to close the valve and to project said locking members to a point where they will engage the lower ends of the casing and prevent upward movement of the plug back into the casing, and packing means carried by the plug above the locking members to form a seal between the exterior surface of the plug and the interior surface of the well easing.

y REUBEN C. BAKER. 

